Caracterização morfofisiológica, molecular, enzimática e compatibilidade vegetativa de Fusarium oxysporum e F. solani em erva-mate

Abstract

The cultivation of Yerba-mate (Ilex paraguariensis) has intensified in the state of Rio Grande do Sul, due to the valorization of the price paid to the producer. However, the demand for studies related to the pathosystem Fusarium x yerba-mate is still insufficient, so that many producers have faced significant losses in the production of the plantations. Given the above, the aim of this study was to characterize the causal agent of rot-of-roots in Yerba-mate (I. paraguariensis). The following specific objectives were established: a) to select efficient morphological characters in the separation of the pathogenic isolates by groups of similarity b) to evaluate the sequencing of different regions of the genome in the identification of the pathogenic isolates at a species level c) to identify the formation of vegetative compatibility groups (VCG) among the pathogenic isolates d) to investigate the enzymatic arsenal of the pathogenic isolates. Therefore, samples were taken in five municipalities of the state, for the pathogen isolation. In addition, soil samples were collected for the area characterization and also for the geo-referencing of collection points. Fusarium spp. isolates were tested for their pathogenicity through substrate inoculation. It was not possible to associate the chemical properties of the soil of the collected areas with the pathogenicity of the isolates in commercial substrates. The 39 isolates were morphologically characterized through the variables of mycelial growth, sporulation, length and width of macroconidia, shape of microconidia, pigmentation of the colonies and formation of chlamydospores. The variables used in the morphological characterization were efficient in the discrimination for seven groups of isolates, especially length of macroconidia associated with sporulation. There were identified seven pathogenic isolates of Fusarium spp. The pathogenic isolates were also identified molecularly by sequencing the ITS, TEF-1 and β-tubulin regions. The sequencing of the ITS, TEF-1α and β-tubulin regions, consolidated the separation between the pathogenic isolates in F. solani and F. oxysporum. For the same isolates, the technique to obtain nit mutants is suitable for henotypic classification, which is fundamental in the VCG tests for Fusarium species. Five VCGs were obtained. The pathogenic isolates of Fusarium spp. produced extracellular enzymes catalase, laccase, cellulase, caseinase, amylase, protease, lipase, polygalacturonase and pectate lyase.